1. Field of the Invention
The present invention relates to a floppy disk drive and more particularly to an improved head supporting mechanism for use in the floppy disk drive, which can cause upper and lower heads to be placed in intimate contact with the opposite recording sides of a floppy disk such that reading/writing can be carried out relative to any one of the recording disk sides.
2. Description of the Prior Art
Although various information recording media have been utilized as external recording elements in computers, a magnetic type disk among them is currently used at present since it is random-accessible and superior in handling. In recent years, there has been developed and is generally used a magnetic floppy disk which is in the form of a flexible plastic sheet having a magnetic recording layer coated thereon at least one side. Such floppy disk is increasingly utilized since it has advantageous in that the floppy disk is inexpensive in comparison with the conventional hard disks and in that the floppy disk can simply and easily be replaced by another to expand the memory capacity of a computer.
A floppy disk having its opposite recording sides requires a double-headed floppy disk drive which can optionally write/read relative to any one of the recording sides of the floppy disk. In such a double-headed drive, it is very important that both two heads can properly be maintained in initimate contact with both the magnetic recording sides of a rotating floppy disk to provide a stable writing/reading operation.
One of such floppy disk drives is disclosed in U.S. Pat. No. 4,151,573 in which a lower head is rigidly mounted on a carriage reciprocatable along the diameter of a floppy disk while an upper head is supported in gimbals fashion by arm means rotatably mounted on said carriage. The upper head is biased to the lower head through the floppy disk by the arm means under the biasing action of a spring. The surface of the lower head serves as a reference surface against which the floppy disk is forced. Thus, any displacement of the floppy disk can be eliminated during operation.
Such a drive of the prior art is advantageous in that a stable operation can always be obtained since the floppy disk is properly positioned by the surface of the lower head. On the other hand, a relatively increased biasing force is required to properly position the floppy disk relative to the reference surface, that is, the surface of the lower head since the latter is rigidly mounted on the carriage. This raises such a problem that excessive wear tends to be produced at the boundary between the floppy disk and the heads.
In spite of the aformentioned stationary reference position, the deviation of the rotating floppy disk cannot completely be absorbed, leading to a modulation in writing/reading.
U.S. Pat. No. 4,379,315 discloses another type head mechanism in which, to overcome the problem in the above-mentioned prior art, a lower head itself is displaciable in the direction perpendicular to the disk surface and in the rotational direction about the diameter of the floppy disk. The lower head also is sufficiently yieldable with respect to the rotation of the head about the circumference of the floppy disk.
The last-mentioned disk drive can follow the dynamic displacement of the rotating floppy disk to provide good operative characteristics. However, this floppy disk drive tends to displace the lower head too much. The lower head may be displaced an increased distance in response to a pressure applied thereto by the rotating disk since the lower head is suspended by a torsion spring. This means that a stable writing/reading operation cannot be obtained.